Rhythmic accompaniment system employing randomness in rhythm generation

ABSTRACT

A system is disclosed for developing rhythmic accompaniment sounds from a free running repetitive ramp waveform having a controllable repetition rate, there being a series of master timing pulses developed by triggering appropriate circuits at different ramp voltage levels during each ramp cycle. Certain of the master timing pulses are selected to form each required rhythmic pattern, the selected pulses being employed to trigger voice circuits to produce desired tones. In one embodiment a pattern selection circuit is employed to permit selective generation of any one of four pattern modes, namely: a first continuously repeated pattern; a second continuously repeated pattern; a pattern in which the first and second patterns are alternated; and a pattern in which the first and second patterns are randomly selected. In the preferred embodiment, 13 master timing pulses are provided during each measure and are separated by 1, 2, or 3 timing units in a 24 timing unit measure, an arrangement which permits of obtaining authentic accompaniment rhythms. A novel cowbell voicing circuit and a novel drum roll control circuit permit rhythmic generation of realistic cowbell and drum roll sounds in response to selected master timing pulses.

Q United States Patent m1 3,629,480

[72] Inventor Michael R- llarris 3,439,569 4/ 1969 Dodds etal 84/126[21] A I N g7 yz gg 3,515,792 6/1970 Deutsch 84/103 o. [22] 55 10, 1970Primary Examiner-Thomas .l. Kozma [45] Patented Dec. 21 1971 AssistantExaminer-Stanley J. Witkowski [73] Assignee D. H. Baldwin CompanyA!trneysW. H. Breumg and Hurvltz & Rose Cincinnati, Ohio ABSTRACT: Asystem is disclosed for developing rhythmic [54] RHYTHM: ACCOMPANIMENTSYSTEM accompaniment sounds from a free running repetitive rampEMPLOYING RANDOMNESS IN RHYTHM waveform having a controllable repetitionrate, there being a GENERATION series of master timing pulses developedby triggering ap- 31 Claims, 11 Drawing Figs propriate circuits atdifferent ramp voltage levels during each 52 U S Cl ramp cycle. Certainof the master timing pulses are selected to 84/l.03, f each requiredrhythmic pattern the sdected pluses 1 Cl being employed to trigger voicecircuits to produce desired nt. tones. [n one embodiment a attemsdection circuit is Field of Sea h 84 0 p re /l. 1, ployed to permitSdective generation f any one f four 103113117126D1G12D1G22D1G23 p r r vv tern modes, namely: a first continuously repeated pattern; a secondcontinuously repeated pattern; a pattern in which the [5613:52;:fsszirss'szszzinz"2:323:32: assives" y s c e n e UNITED STATESPATENTS preferred embodiment, l3 master timing pulses are provided3,546,355 12/1970 Maynard 84/].03 during each measure and are separatedby 1, 2, or 3 timing 3,543,065 12/1970 Freeman 84/103 units in a 24timing unit measure, an arrangement which per-- ,774 12/1970Bunger...... 4/1- mits of obtaining authentic accompaniment rhythms. Anovel 3,549,776 12/1970 Shlga et'al. 4/103 cowbell voicing circuit and anovel drum roll control circuit ,521 2/1969 Park 84/].03 permit rhythmicgeneration of realistic cowbell and drum roll 3,358,068 12/1967 Campbell84/1.03 sounds in response to selected master timing pulses.

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ATTORNEYS PATENTED UECZ] I97? SHEE OUT PUT 3 IDDK TO ream. I PRE-PMP IINVENTDR MHIHREL R. HPRWS ATTO RNEYS RIIYTHMIC ACCOMPANIMENT SYSTEMEMPLOYING RANDOMNESS IN RHYTHM GENERATION BACKGROUND OF THE INVENTIONart. Certain of these are free running, that is, they are neither [0synchronized with nor slaved to the playing of a musical instrument, butrather produce rhythmic accompaniment tones to which the player mayconform his tempo. The free running type accompaniment system iscontrasted to what has become known as the automatic and semiautomaticaccompaniment systems which automatically conform their tempo and/ormeasure duration to the tempo initiated by the player. The presentsystem is of the free running type and is disclosed in a preferredembodiment along with alternative circuitry for providing certainfeatures. Thesystem may be built into a musical instrument, such as anelectronic organ. or may be separate and apart from any musicalinstrument or instruments with which it might be utilized for rhythmicaccompani' ment.

SUMMARY OF THE INVENTION In accordance with one aspect of the presentinvention a rhythmic accompaniment system is actuable to function as afree running rhythm system producing selected rhythm patterns inselected tempos and tone voices and is deactuable to permit the operatorto completely control the tempo and rhythm pattern. When operating inthe free running mode. the system is capable of producing any one orcombination of a plurality of rhythms, each rhythm comprising a twomeasure pattern consisting of two single measure patterns whichalternate continuously. Alternatively, the two patterns may be evokedrandomly if so elected by the operator. A downbeat lamp flashes on thefirst beat of each measure, and means are provided to permit temposelection over a wide range of measures per unit time. Both manual andautomatic operation may be employed either separately or together toachieve desired rhythmic effects.

The system utilizes 13 master timing pulses per measure, the pulsesbeing spaced by integral numbers of fixed time units to provide anoverall l3 pulse measure of 24 timing units duration. In one embodimentthe 13 master timing pulses are derived at corresponding levels of arepetitive ramp waveform, each ramp corresponding to one measure.Alternatively. two ramps are provided during each measure, each rampproducing seven primary pulses of which only six are employed duringalternate half-measures to produce the total of l3 pulses per measure.Depending upon the selected rhythm. various ones of these timing pulsesare chosen during each measure and applied to selected voice circuits toproduce the desired rhythmic sounds.

Some frequently encountered rhythmic patterns extend over two measures.In such patterns the musical part completed by one rhythmic pattern maybe the same for all measures, while another voice in the same patternmay be two measures long. For example, in one type of rhumba pattern thepart played by the bass drum is the same for each measure whereas thepart played by the conga drum is periodic over two measures. Inaccordance with the present invention, provision is made forautomatically alternating two rhythmic measures. and alternativelyforrandomly evoking two different rhythmic measures. In an alternativeembodiment, four pattern modes are actuableby the operator wherein afirst or second rhythmic measure may be continuously repeated, the firstand second rhythmic measures may be continuously alternated, and thefirst and second rhythmic measures may be randomly evoked.

A further provision of the present invention permits adjustment of theslope of the timing ramp to permit the operator to control the measuretime and hence the tempo of the automatic rhythmic accompaniment.

A further feature of the present invention permits resetting of thetiming ramp whenever the system is started to assure that the systemalways starts on the downbeat or first beat of each measure.

In still another feature of the present invention a novel cowbell voicecircuit is provided which gates on a l kHz. oscillator and a linear gatefor 2 kHz. continuous oscillator, the two signals being combined toprovide a realistic cowbell tone.

In still another feature of the present invention certain pulses gatedfrom a rhythm selection matrix are employed to initiate and eventuallyterminate trigger signals applied to drumsimulating voice circuits toproduce drum roll effects over a desired number of beats in eachmeasure.

It is accordingly a broad object of the present invention to provide anovel rhythmic accompaniment instrument.

It is another object of the present invention to provide a rhythmicaccompaniment instrument which is capable of providing rhythmic patternsand voices which are more realistic than those produced by prior artinstruments of this type.

Still another object of the present invention is to provide a rhythmicaccompaniment instrument capable of operation in four different rhythmicmeasure modes, including continuous alternation of two differentrhythmic measures. and the random selection of said two rhythmicmeasures.

Still another object of the present invention relates to the generationof 13 uniquely spaced master timing pulses from which substantially anydesired rhythm pattern can be generated.

Still further objects of the present invention include the generation ofcowbell and drum roll rhythm sounds by means of novel circuitry.

BRIEF DESCRIPTION OF THE DRAWINGS The above and still further objects,features and advantages of the present invention will become apparentupc consideration of the following detailed description of spaembodiments thereof, especially when taken in conjuneuor. with theaccompanying drawings, wherein:

FIG. 1 is a block diagram of a preferred embodiment of the presentinvention;

FIGS. 2a and 2b taken together comprise a schematic circuit diagram ofthe timing circuits of the embodiment illustrated in FIG. 1;

FIGS. 3a and 3b taken together comprise a schematic diagram of therhythm selection matrix employed in the embodiment illustrated in FIG.I;

FIGS. 4a and 4b taken together comprise a schematic cir cuit diagram ofvoice generator circuits utilized in conjunction with the systemillustrated in FIG. 1;

FIG. 5 is a timing diagram illustrating various master timing pulses andrhythmic patterns produced in the system of FIG.

FIG. 6 is a schematic diagram of an alternative circuit for producingthe master timing pulses required for the system of FIG. 1;

FIG. 7 is a schematic diagram of a portion of an alternative matrixcircuit for use in place of the circuit illustrated in FIGS. 3a and b;and

FIG. 8 is a schematic diagram of an alternative circuit to be providedin the system of FIG. I to permit four different modes of a rhythmicpattern operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more particularlyto FIG. 1 of the accompanying drawings there is illustrated a blockdiagram of a rhythmic accompaniment system wherein closure switch S1actuates a repetitive ramp generator 10, the frequency of which isselectively adjustable by means of frequency control element 1]. Theramp signal is applied to a timing pulse generator 13 which provides aplurality of master timing pulses on individual signal lines, at eachpulse provided at a time corresponding to a respective level of the rampsignal provided by generator 10. The master timing pulses occur in arepetitive pattern which comprises a musical measure. The master timingpulses are spaced in time in accordance with the criteria described indetail hereinbelow and are applied to respective lines in a rhythmselection matrix 15. Matrix 15 also receives one or more signals fromautomatic rhythm selection switches 17, matrix 15 being arranged so thatpredetermined ones of the timing pulses are provided as output pulses inaccordance with which of the automatic rhythm selection switches areactuated. The output pulses from matrix 15 are applied to voice circuits19 wherein appropriate accompaniment tones are generated in response toeach output pulse from the matrix. The generated tones are combined andapplied to an amplifier 21 and in turn to loud speaker 23.

Rhythm selection matrix 15 also receives two gating signals from measurealternation control unit 25 which is essentially a bistable device. Whenunit 25 is in a first state it provides a B" signal which causes arhythm selected by switches 17 to be produced in a first rhythmicpattern of output pulses from matrix 15 during each measure. Likewise,when unit 25 is in a second state it provides a C" signal which causesthe selected rhythm to be produced in a second pattern during eachmeasure. The state of the measure alternation control unit 25 isillustrated as being controlled either by downbeat pulse generator 27 orrandom oscillator 29. Downbeat pulse generator 27 receives the rampsignal from repetitive ramp generator and provides a pulse correspondingto the downbeat or first pulse in each measure. This downbeat pulselights lamp 31 at the console of the unit and also changes the state ofmeasure alternation control unit 25. Consequently, when downbeat pulsegenerator 27 is in control of unit 25, the two rhythmic pattern measuresproduced by signals B and C will alternate. Random oscillator 29, wheneffective, changes the state of unit 25 at a frequency which is randomwith respect to the frequency of repetitive ramp generator 10 so thatthe measures produced by signals B and C at matrix change randomly, thatis, not in regular measure alternation.

The Roll oscillator output is fed to the Roll control unit 32 whichresponds to appropriate output pulses applied thereto from matrix 15 toapply a return Roll signal to the matrix. This signal gates one or moreinput signals to the voice circuits 19 for a predetermined period oftime between two master timing pulses supplied by generator 13. Duringthis predetermined period of time the appropriate voice circuitsimulates a drum roll as opposed to the relatively short percussivesound produced by the usual output pulse for matrix 15.

Voice circuits 19 may be actuated manually, either in conjunction withor independently of automatic voice circuit actuation, by appropriatelyactuating various ones of manual rhythm switches 33. lf for example, theclave manual switch is closed, each pedal actuation at console unit 35initiates a trigger pulse, via trigger circuit 37, which passes throughthe pedal clave switch at unit 33 to trigger the clave voice circuit.Actuation ofa key at unit 35 likewise initiates a trigger at circuit 37which passes through the appropriate accompaniment rhythm switch totrigger an appropriate voice circuit at unit 19.

The system of FIG. 1 is illustrated in greater detail in FlGS. 2a, 2b,3a, 3b, and 4a and 4b. With particular reference to FIG. 2a, repetitiveramp generator 10 of FIG. 1 comprises a variable resistor P1 connectedin series with fixed resistor R5 between +28 volts DC and the emitterelectrode of PNP- transistor 01. The collector ofQl is connected viaresistor R1 to the base of NPN-transistor Q3 which, along with O1,comprises a monostable multivibrator. The emitter of Q3 is connecteddirectly to ground and its base is connected to ground via resistor R2.The center arm of variable resistor P1 is connected via resistor RS2 tothe emitter of y PNP transistor Q2, the base of which is connected to+22 v. and the collector of which is returned to ground via timingcapacitor C1. The collector of O2 is also connected to the base ofNPN-transistor 04, the emitter of which is connected to the base offurther NPN-transistor Q5. The emitters of Q4 and OS are returned to 50volts DC through respective resistors R10 and R11. Transistors Q4 and Q5and resistors R10 and R11 comprise a compound emitter follower circuitwhich serves to buffer the linear ramp applied to the base of Q4 fromthe threshold switching circuits Q6-Ql3 connected to the emitter of Q5.Also connected to the collector of O2 is a resistor R6 which is alsoconnected to the collector of Q3 via diode D1 and to a one-half measurebistable circuit, to be described in detail below, via diode D2.

The collector of Q3 and the base of 01 are connected via a seriesconnected resistor R4 and capacitor C2. The collector of Q3 and theemitter of 01 are connected via resistor R3 at +22 v.

Transistor Q2, in conjunction with resistors RS2, P1. and R5, comprisesa constant current generator, the current from which flows from thecollector of 02 at a level depending upon the setting of P1. Theconstant current charges timing capacitor C1 to produce the requiredlinear ramp of voltage at the base of transistor Q4; that is, if C] isinitially uncharged, the voltage thereacross increases linearly.

The linear ramp voltage, which also appears at the emitter of O5, isapplied in parallel to each of resistors R12 through R19, inclusive.Each of R12 through R19 feeds the base of a respective NPN-transistor Q6through Q13 which are connected to progressively increasing (in apositive sense) emitter potentials. More particularly, resistors RS1 andR20 through R33 inclusive comprise a complex voltage divider networkconnected between R5 and ground from which various taps are connected tothe emitters of Q6 through Q13. The potentials connected to the variousemitters vary in accordance with a desired pulse timing sequence suchthat normally nonconducting transistors Q6 through Q13 are gating or. attimes corresponding to predetermined voltage levels of the rampappearing at the emitter of Q5. Nonconduction of Q6 through Q13, in theabsence of the ramp voltage at the emitter of O5, is assured by virtueof the slightly negative voltage appearing at the emitter of 05 viaresistor R11.

The collectors of ()6 through Q12 are AC coupled via capacitors C3through C9 inclusive to the bases electrode of respective NPN-transistorswitches Q14 through Q20, inclusive. Transistors Q14 through Q20 havetheir emitters returned to ground and are biased to normally conductfrom +28 volts DC through their collector-emitter circuits throughrespective collector resistors R51 through R57. This biased-on conditionis accomplished by means of +28 volts DC applied to the bases of Q14through Q20 via respective base-bias resistors R44 through R50. Thecollectors of each of transistors Q14 through Q20 are connected to theanode of respective diodes D5 through D11, the cathodes of which aretied together and connected to the collector of NPN-transistor Q31. Theoperation of Q31 is described in greater detail subsequently; however,for present purposes it is to be understood that when Q31 conducts,diodes D5 through D11 shunt the collectors of Q14 through Q20 to groundand render them unable to provide positive-going output pulses.

As the ramp voltage at the emitter of Q5 increases, Q6 through Q12 aresequentially turned on. The transition from off to on of each ofthesetransistors transmits a corresponding negative-going pulse via couplingcapacitors C3 through C9 to the base of the appropriate transistor Q14through 020, rendering the latter momentarily nonconductive. Thenonconductive intervals from Q14 through Q20 produce positivegoingprimary pulses at the collectors of these transistors, assuming ofcourse that transistor Q31 is not conducting and therefore diodes D5through D11 do not shunt the collectors to ground. Sometime after Q12 isturned on by the ramp signal, Q13 is also turned on, causing O1 toconduct. This effectively tires the monostable circuit comprising Q1,Q3, R1, through R4, and C2. Q3 conducts for approximately 2 millisecondsand thereby discharges timing capacitor C1 via R6 and D1. Discharge ofC1 removes the positive voltage from the emitter of Q5, and each oftransistors Q6 through Q13 are thereby rendered nonconductive. At theconclusion of the interval during which Q3 is conductive, linearcharging of C1 begins again by means of the constant collector currentfrom O2. Sequentially switching of Q6 through Q12 is repeated to providea sequential primary pulses No. 1 through No, 7 at the collectors ofrespective transistors Q14 through Q20.

Pulses are applied to the base of respective NPN-transistors Q51 throughQ63 inclusive. The emitters of these transistors are connected viarespective emitter resistors REl through RE13, inclusive, to 50 voltsDC, the bases being connected via respective base resistors RBI throughRB13, inclusive, to +50 volts DC. In addition the bases of Q51 throughQ63 are connected to the anodes of respective diodes D31 through D43,inclusive, the cathodes of which are connected to the collectors ofdifferent ones of transistors Q14 through Q20. More particularly, thecollector of Q14, which provides primary pulse No. 1, is connected tothe cathodes of D3] and D38. Likewise, primary pulse No. 2 is applied tothe cathodes of D32 and D39, primary pulse No. 3 is applied to thecathodes of D33 and D40, primary pulse No. 4 is applied to the cathodesof D34 and D41, primary pulse No. 5 is applied only to the cathode ofD35, primary pulse No. 6 is applied to the cathodes of D36 and D42, andprimary pulse No. 7 is applied to the cathodes of D37 and D43. Thecollectors of Q51 through Q57, inclusive, are connected to secondarypulse control line I, and the collectors of Q58 through Q63, inclusive,are connected to secondary pulse control line 2. These control linesemanate from a circuit to be described in detail subsequently; howeverfor present purposes it is to be understood that one or the other ofthese control lines, but not both, is at +28 volts DC while the other isat substantially ground poten tial.

In the absence of a positive-going primary pulse applied to its basediode, each of transistors Q51 through Q63 is biased off by the factthat its base junction is shunted to ground by its base diode connectedin series with one of the normally conducting transistors Ql4 throughQ20. A positive-going primary pulse applied to the cathode of any one ofthe diodes D31 through D43 biases that diode off and thereby increasethe voltage at the base of the associated transistor Q51 through Q63. Ifthat transistor has +28 volts DC applied to its collector by theappropriate secondary pulse control line, that transistor is renderedconductive and a positive pulse, corresponding to the positive pulseapplied to its base diode, appears across the emitter resistor of thattransistor. The various signal lines numbered 1 through 13 and connectedto the emitter electrodes of corresponding transistors Q51 through Q63carry secondary pulses, or master timing pulses, to respectivehorizontal lines 1 through 13 of the rhythm selection matrix to bedescribed in detail below in relation to FIGS. 30 and 3b.

Referring now to FIG. 2!; there is illustrated a half-measure bistablecircuit. The half-measure bistable circuit comprises fourNPN-transistors Q21 through Q24, inclusive, interconnected by respectivecoupling resistors and capacitors to pro vide bistable operation. Outputtransistors Q21 and Q24 are always of opposite states in accordance withthe existing state of the half-measure bistable circuit. Secondary pulsecontrol line 1, which as described above is connected to the collectorelectrodes of Q51 through Q57, is derived from the emitter electrode ofQ24. Secondary pulse control line 2, which as described above isconnected to the collector electrodes of Q58 through Q63, is derivedfrom the emitter electrode of Q21. Trigger pulses are applied to thehalf-measure bistable circuit via capacitor C from the collector of Q3each time the master timing ramp waveform is reset. Thus, for alternateI cycles ofthe ramp waveform, the half-measure bistable circuitalternates states, and likewise secondary pulse control lines 1 and 2alternate states. Thus, during one ramp cycle Q51 through Q57 are gatedon by the master timing pulses, and during the next ramp cycle Q58through Q63 are gated on by the primary timing pulses. In this manner,Q51 through Q63 are gated on sequentially over two ramp periods toprovide 13 secondary or master timing pulses. The 13 master timingpulses constitute a musical measure, and consequently two timing rampperiods determine the duration of each measure.

The relative spacing between the master timing pulses is determined byresistors RS1 and R20 through R33 associated with the emitter circuitsof Q6 through Q13. A particular set of values, indicated in thedrawings, yield a preferred timing relationship between these pulsessuch as that illustrated in the top line of the timing diagram in FIG.5. The 13 pulse measure is divided into 24 equal time units, withadjacent master timing pulses being separated by integral numbers ofunits. More particularly, each ramp period or half-measure (during whichpri mary pulses No. 1 through No.7 are generated) is divided into 12equal timing units wherein primary pulses No. l and No. 2 are separatedby three timing units, pulses No.2 and No.3 No. one timing unit, pulsesNo. 3 and No. 4 by two timing units, pulses No. 4 and No. 5 by twotiming units, pulses No. S and No. 6 and pulses No. and No. 7 by onetiming unit each, and pulses No. 7 and No. 1 by two timing units. Sinceprimary pulse No. 5 actuates a transistor only in alternate rampperiods, only six secondary or master timing pulses are generated inalternate half-cycles. Thus, the spacing between master timing pulses 8and 7 is the same as the spacing between primary pulses No. 7 and No. 1,the spacing between master timing pulses 9 and 8 is the same as thespacing between the primary pulses No. 1 and No. 2, etc. The onlydifference between the secondary portion of each measure and the firstportion thereof is the three timing unit spacing between pulses 11 and12, due to the omission of primary pulse No. 5 in the second half of themeasure. Two complete measures of master timing pulses are illustratedin FIG. 5 for reasons to be described in detail below.

As described above, the constant current delivered to timing capacitorC1 to generate the master timing ramp is determined by the setting ofthe center arm of the variable resistor P1. The greater the current theshorter the period of time required for the ramp voltage to trigger eachsuccessive rcsistor Q6 through Q13 and recycle itself. Since the numberof ramps generated per unit time can be controlled in this manner, themeasure time, and hence the tempo ofthe accompaniment system, iscontrolled by means of P1. Resistor RS2, in series with the emitter ofQ2 and the center arm of P1, is preferably selected to provide a tempoof two measures per second when the center arm of P1 is set to theminimum resistance or fast" tempo position.

Because of the wide component tolerance spread effecting the timeinterval between the primary pulses No. 7 and No. 1, it is necessary toselect resistor RS1 in the emitter circuit of Q6 such that the timebetween primary pulses No. 7 and No. l is as desired. As illustrated inthe master timing pulse timing diagram, FIG. 5, RSI is selected toprovide a two timing unit spacing between pulses No. 7 and No. 1, whichis the same spacing as between primary pulses No.4 and No.5.

Each time transistor Q24 in the half-measure of bistable cir cuit isrendered conductive, signifying the start ofa measure, a pulse isapplied via coupling capacitor C11 and resistors R63 and R64 to the baseofa transistor Q25. The collector-emitter circuit of transistor Q25 isconnected in series with an indicator lamp L1 and resistor R91 between+28 volts DC and ground. When pulsed, NPN-transistor Q25 turns on,providing a current path by which lamp L1 may be lit. Capacitor C17 isconnected across lamp L1 to ground to maintain the lamp lit for a periodof about milliseconds at each downbeat or first master timing pulse ineach measure.

It is sometimes desireable to have a rhythm accompaniment of two measureduration; that is the rhythm pattern in alternate measures is somewhatdifferent. The control circuitry for achieving this is illustrated inthe FIG. 2b and includes an alternate bistable circuit comprisingNPN-transistors, Q32 and Q33 interconnected by various resistors andcapacitors to provide conventional bistable operation. A 8" controlsignal is provided from the collector of Q33 and a C" control signal isprovided from the collector of Q32. Depending upon the state of thealternate bistable circuit, one of the B and C control signals is at +16volts DC while the other is at substantially ground. Trigger signals areapplied to the alternate bistable circuit via coupling capacitor C14from the arm of a toggle switch S2. When S2 is in its alternateposition, each pulse through downbeat lamp L1 is conducted through S2and C14 to trigger the alternate bistable circuit. In this mode thealternate bistable circuit is switched by the first timing pulse of eachmeasure and has a switching frequency which is half that of thehalf-measure bistable circuit. Alternatively, with switch S2 in itsrandom position, a trigger is applied to the alternate bistable circuitvia capacitor C14 from a random oscillator circuit comprisingNPNtransistors O34, Q35, and Q36. More particularly, transistors Q34 andQ35 are interconnected by appropriate resistors R84, R85, and R86 andcapacitor C16 provides an oscillatory signal at the emitter of Q35 whichsignal has a low frequency on the order of Hz. This signal is appliedvia resistor R87 to the base of Q36 which has its collector emittercircuit connected in series with the resistor R88 between +22 volts DCand ground. The collector of Q36 thus provides a train of positive-goingpulses of approximately 50 millisecond pulse width and approximately 200milliseconds period. These pulses, with S2 in the random position,trigger the alternate bistable circuit at the 5 Hz. rate, which israndom relative to the frequency of the ramp timing signal. For eitherposition of S2, the B and C control signals alternate state and, in amanner to be described in relation to FIGS. 30 and 3b below, determinethe rhythmic pattern to be produced during each measure.

Also illustrated in FIG. 2b is a stop/start bistable circuit comprisingNPN-transistors Q29 and Q30 interconnected by appropriate resistors andcapacitors to operate in bistable fashion. It is the state of thisbistable circuit which influences the condition of transistor 031 suchthat in one state of the stop/start bistable circuit Q31 is conductiveto shunt the col lectors of Q14 through Q of FIG. 2a to ground viadiodes D5 through D11, thereby inhibiting the primary timing pulses. Inthe other state of the stop/start bistable circuit, transistor Q31 isnonconductive, conduction through diodes D5 through D11 is blocked, andthe master timing pulses are sequentially generated. Stop/start switchS3, a normally open grounding switch, when actuated changes the stateofthe stop/start bistable circuit via triggering capacitor C13 and abounce suppression network including resistors R70 and R71, diode D20and capacitor C19.

A one-shot multivibrator, including NPN-transistors Q26 and Q27 andPNP-transistor Q28 has the function of resetting the timing ramp to itsstart condition whenever the system is started, as by actuation ofswitch S3. The base of Q26 is connected to the collector of Q29 in thestop/start bistable circuit and its collector is connected to +28 voltsDC. The emitter of Q26 is connected to ground via resistor R65 and iscoupled to the base of Q27 via capacitor C12 and resistor R66.Thejunction between capacitor C12 and resistor R66 is connected to thecathode of clamping diode D14, the anode of which is connected toground. The base of Q27 is connected to 50 volts DC via resistor R67.The collector ofQ27 is connected to +28 volts DC via resistor R68 and tothe junction between resistor R6 and diode D1 via diode D2, poled forconduction through the collector-emitter circuit of Q27. The emitterofQ27 is tied directly to the emitter of Q28 and, via resistor R69, tothe collector of Q28. The base of Q28 is connected to the emitter oftransistor O6, in FIG. 2a, Q6 being the first to trigger during eachramp period.

The system is started when transistor Q29 turns off. At this time Q27 isturned on for nominally 6 milliseconds under the influence of capacitorC12 and resistor R66 via buffer Q26. The drop across C12 necessary toprovide the correct transient time for Q27 is achieved by clamping diodeD14 which quiescently (i.e. when 027 is off) clamps one-side of C12substantially to ground potential. When Q27 is conductive, timingcapacitor C1 is discharged via R6, D2, and the collector emittercircuits of transistors Q27 and Q28. This effectively turns off Q6 andassures, for all practical purposes, that the ramp waveform and timingpulses produced therefrom are recycled when the system is started.

To assure that the system starts in the first half of each measure, thepositive transient voltage appearing at the junction of C12 and R66 whenQ29 turns off is employed via resistors R90 and R62 to trigger thealternate bistable and half-measure bistable circuits respectively. Thisassures that the B control signal, at the alternate bistable circuit,and secondary pulse control line 1, at the half-measure bistablecircuit, are rendered positive when the system starts.

Stop/start switch S3 is described above as being effective to stop orstart the automatic rhythm accompaniment tones of the present invention.S3 is preferably a foot switch which when employed to stop theaccompaniment effectively shunts the timing pulses to ground via diodeD5 through D11 as described. Note however that the timing circuit isstill opera tive in the sense that the master timing ramp sequentiallyactuates 06 through 013. In order to completely disable the mastertiming circuit, switch S], which is ganged to variable resistor P1, isopened to thereby apply 50 volts DC to the collectors of Q4 and Q5 viaresistor R93. This effectively cuts off Q4 and Q5 and preventsapplication of the ramp voltage to Q6 and through Q13. Since 013 isprevented from triggering Q1 and Q3, timing capacitor C1 cannotdischarge and the repetitive ramp pattern is terminated. Opening of 51also drives the collector of transistor Q29 of the stop/start bistablecircuit negative via diode D19 and resistor R93 so that Q29 ismaintained off. If S1 is now closed, Q4 and Q5 are enabled and currentflows into C1 to reinitiate the repetitive ramp waveform.

Resistor R72 connected between the base of the emitter of 030 in thestop/start bistable circuit serves as a bias during turn on of thesystem power supply such that the system settles in a condition wherebyQ31 is conductive to inhibit the prima ry timing pulses from 014 throughQ20.

There is also provided in FIG. 2b a roll oscillator comprisingNPN-transistors Q39 and Q40 interconnected by appropriate resistors andcapacitors to provide an oscillatory output signal at a frequency ofapproximately 25 Hz. This signal, taken from the collector of Q40, isapplied to the base of PNP-transistor Q41, the emitter of which isconnected to +28 volts DC and the collector of which is connected to acommon junction from which the brush roll control signal (via resistor Rand diode D14) and snare roll control signal (via resistor R81 and diodeD15) are provided, these signals being positive pulses at the 25 Hz.rate if Q41 is not inhibited. Said common junction is coupled via diodeD18 to the collector of NPN-transistor 037 which, along withNPN-transistor Q38 and appropriate resistive and capacitiveinterconnecting circuitry, comprises a roll control bistable circuit. Inone state of the roll control bistable circuit 037 is conductive toground, effectively shorting out the brush and snare roll controlsignals. In the opposite state of the roll control bistable circuit Q38is conductive and Q37 is not, thereby rendering the brush and snare rollcontrol signal operative to effect the appropriate simulated drum rollsas described hereinbelow. The state of the roll control bistable circuitis determined by the roll start signal applied to the base of Q38 andthe roll finish signal applied to the base of Q37, both of which signalsare received from the rhythm selection matrix described in detail inreference to FIGS. 3a and 3b. The roll start signal triggers Q38 on andQ37 off to enable the brush and snare roll control signals; the rollfinish signal triggers 037 on to inhibit the brush and snare rollcontrol signals.

Before describing the rhythm selection matrix, brief mention should bemade of the shush 1 and shush 2 signals. Shown is a term which refers tothe background noise appropriate to some rhythm accompaniments. Shush lis a consistent noise level realized by connecting R7 to a suitablevoice circuit in the manner described hereinbelow with reference toFIGS. 4a and 4b. Shush 2 refers to a noise character which decreasesthrough the beginning portion of the measure until reaching a consistentlevel at the middle of the measure, which level is retained until themeasure is completed. This is realized by mixing a steady noise signal,set up by RS, and a noise signal having a triangular envelope during thefirst half of the measure, and employing only a steady level during thesecond half of the measure. More particularly, the triangular envelopeis generated from the master timing ramp during a first ramp cycle viaresistor R9 connected to the emitter of 05. During the next ramp cyclesecondary pulse control signal 2, provided by the emitter of Q21, issupplied by diode D4 to override the ramp signal and provide a steadylevel for the shush 2 signal.

Referring now to FIGS. 3a and 3b of the accompanying drawings, there isillustrated a resistive matrix in which the horizontal lines are 13 innumber, corresponding to the 13 master timing pulses which are appliedthereto and which are illustrated in the top line of each measure inFIG. 5. A total of 47 vertical matrix lines are illustrated, thevertical lines being divided into eight groups representing differentrhythms. The number of rhythm groups illustrated is by way of exampleonly and not to be considered limiting on the scope of the presentinvention. Vertical lines and horizontal lines are selectivelyinterconnected at appropriate junctions by 100 K resistors so that asignal is provided on each vertical line in time coincidence with apulse on a horizontal line to which that vertical line is resistivelycoupled. Thus, for example, vertical line 1 is seen to be resistivelycoupled to horizontal lines 1, 4, 7, 8, II and 13, indicating thatduring each measure the I, 4, 7, 8, l1, and 13 master timing pulsesappear on vertical line 1. Likewise vertical line 29 is resistivelycoupled to the 4 and 8 master timing pulse lines to thereby provide the4 and 8 master timing pulses during each measure,

The groups into which the vertical lines are divided are as fOlIOWSl TheLATIN III rhythm can represent the cha-cha, mambo, or samba according tothe tempo selected by variable resistor P1. The other rhythms are selfevident.

Each vertical line l-47 is connected to the anode of a respective diodeD14 through D60, respectively. The cathodes of D14 through D18, in theSWING rhythm group, are connected to one pole ofa two-pole SWING switchwhich, when not actuated effectively grounds the cathodes of thesediodes and thereby shunts positive pulses appearing on vertical lines1-5 to ground. When actuated the SWING switch leaves the cathodes of D14through D18 floating, thereby enabling vertical lines lto conduct theirresistively coupled master timing pulses further along the circuit.Likewise, the diodes associated with the BALLAD lines 6 through 11 areshorted to ground by one pole of the BALLAD switch unless the latter isactuated. Similar selective shorting of the vertical lines in the ROCK,WALTZ, BOSSA NOVA, RHUMBA, LATIN II, and MARCH groups is accomplished byrespective automatic rhythm switches. Thus by actuating the appropriateautomatic rhythm switch a group of vertical lines corresponding to theselected rhythm are enabled.

The sequential pulses appearing on the vertical lines are connected tovarious appropriate voice circuits of FIGS. 4a and 4b, described indetail hereinbelow. The voice circuits respond to application ofpositive trigger pulses thereto to produce rhythmic sounds whichsimulate those produced by musical accompaniment instruments. Thus, andthe inclusion of the following circuits is by no means limiting, thereare provided the following voice circuits connected to respond to thetriggers produced by the matrix of FIGS. 3a and 3b: Cymbal, Snap, Snare,Bass Drum, Clave, Cowbell, and Conga Drum. The Cymbal trigger line isresistively coupled to vertical lines 5, I7, 26, and 47 of the rhythmselection matrix. The snap trigger line is a combination of the Snap A,Snap B, Snap C signals. (Snap," used herein interchangeably with Brush,refers to the sound produced by striking a brush stick on a drum or theoperation ofa Hi-Hat.) The snap A signal is connected directly to theSnap trigger line and receives pulses from vertical lines 6, l2, 18, 21,27 and 35 of the matrix. The Snap B signal is selectively gated to theSnap trigger line by means of series diode 87 and shunt diode 86, thecathode of the latter being connected to the B control signal providedby the alternate bistable circuit in FIG. 2b. When the B control signalis positive, diode D86 is blocked and the Snap B signal is conductedthrough diode D87 to the Snap trigger line. When the B control signal isgrounded diode D86 shunts pulses appearing on the Snap B line to groundand inhibits their application to the Snap trigger line. The Snap Bsignal is derived from vertical line number 1 of the matrix.

A Snap C signal is applied selectively to the snap trigger line via adiode gate comprising series diode D89 and shunt diode D88, the cathodeof the latter being connected to the C control signal provided by thealternate bistable circuit of FIG. 2b. When the C control signal ispositive D88 is blocked and the pulses appearing on the Snap C line areconnected to the Snap trigger line. When the C control signal isgrounded D88 acts to shunt all Snap C signals to ground and preventtheir conduction to the Snap trigger line. Thus, depending upon thestate of the alternate bistable circuit of FIG. 2b, either the pulsesappearing on the Snap B line or those appearing on the Snap C line areconducted to the snap voice circuit via the Snap trigger line during anygiven measure. The Snap A pulses, however, are conducted to the Snapvoice circuit during every measure, irrespective of the state of thealternate bistable circuit.

In like manner, there are provided, by means of various combinations ofthe vertical lines in the matrix, Snare A, Snare B, Snare C, Bass A,Bass B, Bass C, Clave B, Clave C, Cowbell A, Cowbell B, Cowbell C, CongaA, Conga B, and Conga C signal lines, which apply pulses to theirrespective voice circuits. All of the pulses appearing on a B triggerline are gated through to their respective voice circuits only when theB control signal from the alternate bistable circuit is positive.Likewise, all of the pulses appearing on a C trigger line are gatedthrough to their respective voice circuits only during measures in whichthe C control signal provided by the alternate bistable circuit ispositive. The signals are applied to their respective voice circuitsduring every measure.

In addition, vertical lines 10 and 44 of the matrix are combined toprovide the roll start signal, which is applied to the base of Q38 inthe roll control bistable circuit of FIG. 2b. Likewise, vertical linesI1 and 45 are combined to provide the roll finish signal, applied to thebase of 037 in the roll control bistable circuit. The brush and snareroll control signals provided at the collector of Q41 are connected tothe Snap A and Snare A lines respectively to provide a repetitivepositive voltage to these signal lines, and thereby to theircorresponding voice circuits, whenever a roll is to be simulated.

Each of the SWING, BALLAD, and WALTZ automatic rhythm switches have anextra pole ganged thereto for purposes of providing shush effects. Moreparticularly, the shush 1 signal is applied to the second pole of theSWING switch which, when actuated, applies to the shush 1 signal to theCymbal voice circuit, to be described below in reference to FIGS. 4a and4b. The second pole of the BALLAD and WALTZ automatic rhythm switchesselectively apply the shush 2 signal to the Cymbal voice circuit.

Operation of the matrix of FIGS. 30 and 312 may best be illustrated withreference to the timing diagram of FIG. 5. Using as an example the SWINGrhythm, for which we assume that the SWING automatic rhythm switch hasbeen actuated, the Bass A signal is pulsed by the first, fourth, eighth,and I lth master timing pulse during each measure, these pulses beingequally spaced (by six timing units) to provide the standard four beatsto the measure required for the SWING rhythm.

The Snap trigger line is pulsed by the Snap B signal during B measuresat the first, fourth, seventh, eighth, llth and 13th master timingpulses, and by the Snap C signal during C measures at the first, fourth,eighth, 10th, llth and 13th master timing pulses. Thus, when thealternate bistable circuit of FIG. 2b operates in its alternate mode,during alternate measures, the Snap voice circuit is triggered bydifferent pulse patterns in each measure. Also for the SWING rhythm itis seen that the Bass C signal pulses the base voice circuit during Cmeasures at the seventh master timing pulse to provide an effectiveprebeat (by the Bass Drum) before the third pulse of alternate measures.In addition, the Cymbal voice circuit is triggered by the fourth and I1th master timing pulse of each measure.

To illustrate the effects of the roll control circuits, reference ismade to the BALLAD rhythm mode wherein master timing pulse 1 appears onvertical line 10 of the matrix to provide a roll start pulse at thestart of each measure. The roll start pulse turns off 037 at the rollcontrol bistable circuit of FIG. 2b to thereby enable the brush andsnare roll control signals. The snare roll control has no effect at thistime since it is connected to D56 and thereby shunted to ground via theMARCH automatic rhythm switch. However the brush roll control signal isapplied to vertical line 6 to provide a Snap A signal. This signal keepsthe Snap A line pulsed at 25 cps. for as long as the brush roll controlsignal is present. This condition obtains until the occurrence of pulsefour, at which time the roll finish pulse is generated via vertical line11 of the matrix to turn on transistor Q37 in the roll control bistablecircuit. This inhibits the brush roll control signal which is therebyremoved from the Snap A trigger line. The positive voltage appearing onthe Snap trigger line during the interval between pulses l and 4 of eachmeasure cause the Snap voice circuit to produce a characteristic brushroll sound over that interval during each measure.

The particular choice of 24 basic timing units in each measure permitaccurate and realistic rhythmic patterns to be produced by the presentsystem. More particularly, since 24 is readily divisible by two, three,four, 6, six, eight and 12, a larger variety of basic rhythms arereadily reproducible. For example, 4 beats to a measure, as required bythe BALLAD, SWING, etc., is readily provided by simply utilizing pulsesl, 4, 8, and II in each measure, these pulses being separated by sixtiming units each. Three beats per measure, as required by the WALTZ, isreadily achieved by means of pulses l, 5, and 10, separated by 8 timingunits each, in each measure. A faster waltz, though not provided forexpressly by the circuitry illus trated and described herein, canlikewise be reproduced by utilizing pulses l, 3, 5, 8, l and anadditional master timing pulse between pulses 11 and 12, spaced twotiming units from pulse 11. The variety of selectable rhythms is thussubstantially unlimited by virtue of the particular timing arrangementselected.

The system as described heretofore is adapted to be built into a musicalinstrument such as an electronic organ, and as such must be adapted topermit manual keying of the various voice circuits when automatic rhythmaccompaniment is either not desired, or of itself is not sufficient toproduce the desired effects. To this extent, each of the voice circuitsmay be triggered via specially provided manual rhythm switches (FIG. 4a)such as the bass pedal, brush pedal, clave pedal, cymbal pedal, brushaccompaniment, snare accompaniment, conga accompaniment, and cowbellaccompaniment switches. The pedal switches receive a pedal triggergenerated in a manner described hereinbelow and, when actuated, applythis trigger to the corresponding voice circuits of FIGS. 4a and 4b. Theaccompaniment switches are operative to apply accompaniment triggers,generated in the manner described hereinbelow, to corresponding voicecircuits. These manual rhythm switches are operative in conjunction withan on/off button which; in the off position, shunts the accompanimentand pedal trigger signals to ground and which, in the on position,permits application of these trigger signals to the appropriate voicecircuits.

Referring still to FIGS. 4a and 4b there is illustrated an accompanimenttrigger amplifier comprising transistors Q20 and Q21 connected inmonostable multivibrator configuration. Actuation of appropriate keys atthe keyboard of the electronic organ provides a signal to theaccompaniment input terminal which triggers the monostable circuit toprovide an accompaniment trigger pulse to four of the manual rhythmswitches. The accompaniment trigger pulse is approximately +22 volts inamplitude and has, nominally, a 5 millisecond duration. Likewise a pedaltrigger amplifier is illustrated and is similar to the accompanimenttrigger amplifier except that two mutually exclusive input circuits areprovided. One of these is used in conjunction with the monophonic pedallatch system and the other with a polyphonic system. When triggered, thepedal trigger amplifier, comprising a one-shot multivibrator includingtransistors Q22 and 023, provides an output pulse of the same generalcharacter as the accompaniment trigger. The pedal trigger is alsoapplied to four of the manual rhythm switches as described above.

The cymbal, snap (brush) share drum, bass drum, clave and conga drumvoice circuits are conventional in nature, each responding to an inputtrigger applied thereto for providing a percussive tone simulating thesound signified by the name of the voice circuit. For example, the clavesound simulates two hard wooden rods struck together. A trigger receivedat the base of transistor Q12 of the clave circuit gates 012 on for theduration of the trigger pulse. This renders Q13 conductive and gates onthe gated oscillator configuration including transistor Q13 to provide asinusoidal signal of decaying amplitude and of such frequency tosimulate the clave sound. The decay period is determined by resistor R34and capacitor C23 connected in series between the emitter of Q13 andground. Similar operation ensues in each of the cymbal, snap, snaredrum, bass drum, and conga drum circuits, wherein gated oscillator ofapproximate frequency is triggered on by a transistor switch in responseto each applied voice trigger pulse. The oscillator amplitude thendecaysupon removal of the trigger pulse. The triggers received by eachof the conga drum, clave bass drum, cymbal and snare drum voice circuitare the appropriate automatic triggers supplied by the matrix of FIGS.3a and 3/2, or by the accompaniment or pedal triggers supplied by themanual rhythm switches in FIG. 4a. The Snap voice circuit receives threetriggers, namely the brush accompaniment and the brush pedal trigger, aswell as the automatic trigger provided by the matrix. The brush or snapvoice circuit may thus be triggered manually by either pedal or keyactuation.

A novel voice circuit included in FIG. 4b is the cowbell voice circuitwhich, when triggered, provides a combined 1 kHz. and 2 kHz. decayingtone, the frequency of the 2 kHz. signal being prevented from shiftingduring the decay of the tone. The cowbell circuit includes a gated 1kHz. oscillator comprising NPN-transistor transistor Q17 and associatedresistors and capacitors connected to produce the 1 kHz. oscillatorysignal at the emitter of Q17 whenever gating transistor 018 is triggeredon by an input trigger. To this extent, the 1 kHz. signal is actuated asin the other voice circuits. Thus, when triggered, Q18 remains on forthe duration of the trigger pulse, gating on the 1 kHz. oscillator viaresistor R52 and diode D3. Upon termination of the trigger pulse, Q18turns off but the 1 kHz. signal is sustained at a decaying amplitudeover a sustan period determined by capacitor C36 and resistor R52. Thegated decaying 1 kHz. signal is applied to a common voice circuit outputline via resistor R65 and capacitor C44.

The 2 kHz. oscillator in the cowbell voice circuit comprisesNPN-transistor Q16 and associated resistive and capacitive elementsinterconnected to provide a continuously running 2 Hz. oscillator. The 2kHz. signal is applied via capacitor CS8 to a linear gate which includesdiodes D4 and D5, capacitor C38, and resistors R56 and R57. Whenconductive, the linear gate applies the continuous 2 kHz. signal to thecommon voice circuit output line via resistor R66 and capacitor C45.When 018 is gated on by an input trigger pulse, PNP-transistor Q19experiences a reduction in base voltage which renders it conductive.This supplies gating current via resistor R55 to the linear gate,turning the latter on and permitting passage therethrough of the 2 kHz.signal. Conduction of current through 019 also charges capacitors C37.When the input trigger applied to the base of 018 terminates, the latterturns off and in turn renders 019 nonconductive. The linear gate remainson due to the charge existing on capacitor C37, which now dischargesthrough two resistive paths, one of which includes R57, D4 and R58, theother of which includes R56, D5 and R59. The amplitude of the 2 kHz.signal applied through the linear gate to the common output linedecreases as C37 discharges until eventually the linear gate is cut offand the 2 kHz. tone terminates. Importantly, the linear gate (linear inthe sense that no distortion of the 2 kHz. signal is produced whenpassed therethrough) is required to prevent frequency shift of the 2kHz. signal, which shift would alter the character of the cowbell toneto produce something which is not realistic.

the output signals from all of the voice circuits are tied to a commonoutput line which is connected to the center arm of the volume control,a variable resistor connected between the input terminal to thepedalpreamplifier and ground.

Generation of the shush 1 and shush 2 signal proceeds when appropriateones of the automatic rhythm switches are actuated as described inrelation to FIG. 312. More particularly the shush output line from theautomatic rhythm switches is connected to the cathode of diode D2, theanode of which is connected to transistor 06 in the cymbal voicecircuit. When an appropriate automatic rhythm switch is closed, thecommon shush line, in combination with the actuated switch and either ofthe shush 1 or shush 2 lines, provide a path for emitter current throughdiode D2 for transistor 06. The latter conducts to feed suitable signalvia the cymbal voice circuit (based on transistor 09) to providecymballike noise at the system output unit for as long as the shush 1 orshush 2 signals are selected by the automatic rhythm switches. Note thatthe shush signals are not derived from rhythmic pulses gated through therhythm selection matrix but rather are continuous sounds generatedthroughout each measure. A shush inhibit signal applied to diode D1 inFIG. 4a from the collector of transistor 030 in stop/start bistablecircuit of FIG. 2b prevents generation of a shush signal when theautomatic rhythm system is off. More particularly, when the system isoff, transistor 030 in the stop/start bistable circuit is nonconductiverendering the shush inhibit signal positive. This biases diode D1 on atthe cymbal voice circuit and applies a positive voltage to the cathodeof diode D2, which voltage is greater than the quiescent voltage at thebase of transistor 06. This prevents transistor 06 from conducting aslong as the shush inhibit is positive; therefore no shush signals can begenerated at this time.

Referring now to FIG. 6 of the accompanying drawings there isillustrated an alternative approach to generating the master timingpulses in the system of the present invention. In the above-describedembodiment there are two ramp signals generated for each measure, whichresults in the generation of seven primary pulses. These pulses areappropriately gated during alternate half-measures to produce 13 mastertiming pulses per measure. In the circuit of FIG. 6 the approach is togenerate one linear ramp per measure, which ramp triggers all 13 mastertiming pulses directly, in the same manner as the seven primary pulsesare triggered in the FIG. 2a. More particularly, the circuit of FIG. 6includes a constant current source based on transistor 0102 which isdirectly analogous to the constant current source which includestransistor 02 of FIG. 2a. Likewise, the reset monostable circuit for theramp generator includes transistor 0101 and 0103, analogous totransistors 01 and 03 of FIG. 20. Also provided is an emitter followerbuffer circuit including transistors 0104 and 0105, analogous totransistors 04 and 05 of FIG. 2a. The values of the various resistorsand capacitors associated with transistors 0101 through 0105 differ fromthe values of the components employed with transistors 01 through 05 ofFIG. 2a, primarily because of the nature of the ramp generated in FIG. 6which ramp must have a duration of twice that of the ramp of FIG. 2a.The emitter of 0105 is coupled in parallel to the base of each of l4transistors 0111 through 0124. These latter transistors are normallynonconducting and are triggered into conduction at respective increasingvoltage levels of the linear ramp signal appearing at the emitter of0105. Transistor 0124, which is driven into conduction last of alltransistors 0111 through 0124 during each ramp period resets the rampsignal by triggering the reset monostable circuit comprising 0101 and0103. As each of0111 through 0123 is driven into conduction a triggerpulse is AC coupled to a respective one of pulse generators 111 through123, all of which are identical, only generator 123 being illustrated indetail. Each of the pulse generators includes a pair of NPN-transistors0125 and 0126 connected in cascade, with the input trigger being appliedto the base of0125 and the output signal taken from the emitter of 0126.0125 is normally conducting and 0126 is normally nonconducting. Whentransistor 0123, for example, is driven into conduction by the inputramp, a negative going transition appears at the collector of 0123 whichis coupled via an input coupling capacitor to the base of0125 to turnthe latter off. Voltage at the collector of 0125, and hence at the baseof 0126, increases, rendering 0126 conductive to provide apositive-going pulse at the emitter electrode of 0126. This pulse is themaster timing pulse provided by the pulse generator.

The 13 master timing pulses produced by pulse generators 111 through 123are preferably spaced, as determined by the emitter biases fortransistors 0111 through 0124, in the manner illustrated in the top lineof the timing diagram of FIG. 5. As described, this particular spacingpermits generation of authentic rhythm patterns not previouslyattainable in prior art rhythm systems. While other techniques forgenerating desired master timing pulse patterns may be employed in thescope of the present invention, those techniques described in relationto FIGS. 2a and 6 are believed the simplest and the most easilyeffected.

Referring now to FIG. 7 of the accompanying drawings there isillustrated an alternative approach to providing a rhythm selectionmatrix for performing the same function as the matrix illustrated inFIGS. 3a and 3b. More particularly, the 13 input timing pulses areapplied to horizontal lines of the matrix just as in FIGS. 3a and 3b,and the vertical lines of the matrix are selectively resistively coupledwith the various horizontal lines and grouped in accordance with theparticular selected tempos. Whereas selection of the tempo in FIGS. 3aand 3b is achieved by ungrounding respective groups ofdiodes D14 throughD61 by means of the automatic rhythm switches, in FIG. 7 the shuntdiodes are eliminated and replaced by respective series sections of eachautomatic rhythm switch. Thus actuation of the SWING automatic switchcloses 5 switches in series with vertical lines 1 through 5 to enablethe selected master timing pulses resistively coupled to these lines tobe applied to the various voice circuit trigger lines.

It is to be stressed at this point that although the trigger patternsgenerated for each rhythm in FIGS. 3a and 3b are identical to thepatterns selected in the circuit of FIG. 7, the particular patternsillustrated in FIG. 5 are not limiting as to the scope of the presentinvention. For example, it may be desirable to additionally generate aSnap A pattern for the SWING rhythm or eliminate the Snap C pattern inthat rhythm. Numerous combinations are of course applicable to produceother desired rhythmic effects. The patterns illustrated in conjunctionwith the matrices in FIG. 3b and 3a and FIG. 7 and in the timing diagramof FIG. 5 are believed to be most authentic in so far as simulation ofstandard rhythm patterns are concerned. Likewise, additional rhythmpatterns other than the eight illustrated in conjunction with FIGS. 5and 3a and 3b may be provided by the techniques disclosed, theirauthenticity in simulating actual standard rhythm patterns beingfacilitated by the particular choice of master timing pulse spacingprovided herein.

Referring now to FIG. 8 of the accompanying drawings there isillustrated a modified control circuit for providing greater flexibilityin selecting measure patterns than is possible in the embodimentdisclosed above. More particularly, there is illustrated in FIG. 8 thealternate bistable circuit, substantially identical to that illustratedin FIG. 2b, having a control switch S2 identical to that in FIG. 2b fromwhich the state of the alternate bistable circuit may be controlled,either by the random oscillator or the downbeat signal as described inrelation to FIG. 2b. In addition there is provided a switch S6schematically illustrated as having three positions, namely an offposition, a B position, and a C position. In the B position switch S6grounds the collector of Q32 of the alternate bistable circuit and inthe C position grounds the collector of Q33. If the collector of 032 isgrounded the collector of Q33 is at a positive voltage and the B patternis continuously produced by the matrix as long as S6 is in thisposition. When S6 grounds the collector of Q33, in a similar manner, theC pattern is continuously produced. The addition of switch S6 thereforeprovides four different pattern modes, each capable of selection by theperformer. These modes are:

I. with S6 in the B position, regardless of the position of S2, the Bpattern is continuously produced during each measure;

2. with S6 in the C position, the C pattern is continuously produced,regardless of the position of S2, during each measure;

3. with S6 in the off position and S2 in the alternate position patternsB and C alternate during successive measures;

4. with S6 in the off position and S2 in the random position, patterns Band C are switched at a random rate relative to the repetition rate ofthe measures in accordance with the random triggering from the randomoscillator, thereby producing a continuously varying rhythm pattern.

Thus two different single measure patterns may be produced or alternatedor randomly selected in accordance with the settings at S2 and S6.

The B control and C control signals provided at respective collectors oftransistors Q33 and Q32 may be employed as illustrated in FIGS. 3b togate the various trigger lines at the output of the matrix.Alternatively these signals may be employed directly at the inputcircuits of each of the voice circuits of FIGS. 4a and 4b, asillustrated in FIG. 8. By way of example, the Snap voice circuitillustrated in FIG. 8 and the Snap B and Snap C trigger lines areillustrated as being con nected to the anode of respective diodes D101and D102, the cathodes of which are connected to respective collectorsof transistors Q33 and Q32. When the B control signal is high and the Ccontrol signal grounded, diode D101 is blocked and Snap B pulses areapplied directly to the Snap voice circuit; diode D102 is grounded andthereby shunts the Snap C triggers to ground. Alternately, when the Ccontrol voltage is high, diode D102 is blocked permitting application ofSnap C triggers to the Snap voice circuit; D101 shunts the Snap Btriggers to ground.

While I have described and illustrated specific embodiments of myinvention, it will be clear that variations of the details ofconstruction which are specifically illustrated and described may beresorted to without departing from the true spirit and scope of theinvention as defined in the appended claims.

I claim:

1. In a rhythm accompaniment instrument of the repetitive 'rhythm type:

means for generating at least first and second patterns of pulses, eachof said patterns having a period corresponding to a measure of music;

generator means responsive to application of pulses thereto forgenerating corresponding rhythmic sounds; and control means for randomlyapplying said first and second patterns of pulses to said generatormeans.

2. The combination according to claim 1 wherein said con trol meanscomprises:

bistable means having first and second stable states;

means for switching said bistable means between said first and secondstable states at a frequency which is greater than that of said measuresof music; and

gating means responsive to said bistable means in said first stablestate for passing said first pattern of pulses to said generator meansand inhibiting passage of said second pattern of pulses to saidgenerator means, and responsive to said bistable means in said secondstable state for passing said second pattern of pulses to said generatormeans and inhibiting passage of said first pattern of pulses to saidgenerator means.

3. The combination according to claim 1 wherein said control means isselectively actuable to each of at least two discrete states for:

a. in a first state randomly applying said first and second patterns ofpulses to said generator means; and

b. in said second state alternately applying said first and secondpatterns of pulses to said generator means during respective alternatemeasures of music.

4. In a rhythmic background instrument of the repetitive rhythm type:

timing means for providing at least first and second patterns of pulses,each of said patterns having a period corresponding to a measure ofmusic;

generator means responsive to application of pulses thereto forgenerating corresponding rhythmic sounds; and

control means selectively actuable to each of at least three discretestates for:

a. in a first state applying only said first pattern of pulses to saidgenerator means during each measure of music;

b. in a second state alternately applying said first and second patternsof pulses to said generator means during respective alternate measuresof music; and

c. in a third state randomly applying said first and second patterns ofpulses to said generator means.

5. The combination according to claim 4 wherein said control means isactuable to a fourth discrete state for applying only said secondpattern of pulses to said generator means during each measure.

6. The combination according to claim 4 wherein said timing meanscomprises:

first means for repetitively providing a sequence of master timingpulses;

a matrix comprising a first plurality of conductors, a second pluralityof conductors and means for conductively coupling predetermined ones ofsaid first plurality of conductors to predetermined ones of said secondplurality of conductors;

means for applying said master timing pulses to respective conductors insaid first plurality of conductors;

means for connecting predetermined ones of said second plurality ofconductors together to form a plurality of common circuit junctions; and

means for coupling selected ones of said common circuit junctions tosaid generator means under control of said control means.

7. The combination according to claim 6, further comprising:

means for selectively rendering predetermined groups of said secondplurality of conductors nonconductive relative to said common circuitjunctions.

8. The combination according to claim 7 wherein said lastmentioned meanscomprises:

a plurality of diodes, one each connected to a respective conductor insaid second plurality of conductors;

a plurality of switch means, one each operatively associated with arespective one of said predetermined groups of said second plurality ofconductors, each switch means being actuable for shorting to ground allof the conductors in its operatively associated groups via said diodes.

9. The combination according to claim 7 wherein said lastmentioned meanscomprises a plurality of manually actuable multisection switches, eachswitch section being connected in

1. In a rhythm accompaniment instrument of the repetitive rhythm type:means for generating at least first and second patterns of pulses, eachof said patterns having a period corresponding to a measure of music;generator means responsive to application of pulses thereto forgenerating corresponding rhythmic sounds; and control means for randomlyapplying said first and second patterns of pulses to said generatormeans.
 2. The combination according to claim 1 wherein said controlmeans comprises: bistable means having first and second stable states;means for switching said bistable means between said first and secondstable states at a frequency which is greater than that of said measuresof music; and gating means responsive to said bistable means in saidfirst stable state for passing said first pattern of pulses to saidgenerator means and inhibiting passage of said second pattern of pulsesto said generator means, and responsive to said bistable means in saidsecond stable state for passing said second pattern of pulses to saidgenerator means and inhibiting passage of said first pattern of pulsesto said generator means.
 3. The combination according to claim 1 whereinsaid control means is selectively actuable to each of at least twodiscrete states for: a. in a first state randomly applying said firstand second patterns of pulses to said generator means; and b. in saidsecond state alternately applying said first and second patterns ofpulses to said generator means during respective alternate measures ofmusic.
 4. In a rhythmic background instrument of the repetitive rhythmtype: timing means for providing at least first and second patterns ofpulses, each of said patterns having a period corresponding to a measureof music; generator means responsive to application of pulses theretofor generating corresponding rhythmic sounds; and control meansselectively actuable to each of at least three discrete states for: a.in a first state applying only said first pattern of pulses to saidgenerator means during each measure of music; b. in a second statealternately applying said first and second patterns of pulses to saidgenerator means during respective alternate measures of music; and c. ina third state randomly applying said first and second patterns of pulsesto said generator means.
 5. The combination according to claim 4 whereinsaid control means is actuable to a fourth discrete state for applyingonly said second pattern of pulses to said generator means during eachmeasure.
 6. The combination according to claim 4 wherein said timingmeans comprises: first means for repetitively providing a sequence ofmaster timing pulses; a matrix comprising a first plurality ofconductors, a second plurality of conductors and means for conductivelycoupling predetermined ones of said first plurality of conductors topredetermined ones of said second plurality of conductors; means forapplying said master timing pulses to respective conductors in saidfirst plurality of conductors; means for connecting predetermined onesof said second plurality of conductors together to form a plurality ofcommon circuit junctions; and means for coupling selected ones of saidcommon circuit junctions to said generator means under control of saidcontrol means.
 7. The combination according to claim 6, furthercomprising: means for selectively rendering predetermined groups of saidsecond plurality of conductors nonconductive relative to said commoncircuit junctions.
 8. The combination according to claim 7 wherein saidlast-mentioned means comprises: a plurality of diodes, one eachconnected to a respective conductor in said second plurality ofconductors; a plurality of switch means, one each operatively associatedwith a respective one of said predetermined groups of said secondplurality of conductors, each switch means being actuable for shortingto ground all of the conductors in its operatively associated groups viasaid diodes.
 9. The combination according to claim 7 wherein saidlast-mentioned means comprises a plurality of manually actuablemultisection switches, each switch section being connected in serieswith a respective conductor in said second plurality of conductors, eachswitch being operatively associated with a respective one of saidpredetermined groups Of said second plurality of conductors for openingand closing all of the switch sections for that group in unison.
 10. Thecombination according to claim 6 wherein said first means comprises:means for providing a repetitive ramp signal waveform, each ramp signalperiod corresponding to one-half measure of music; means responsive tosaid ramp signal achieving respective amplitudes for generating asequence of primary pulses during each ramp signal period; and means forgating predetermined ones of said primary pulses during alternate rampsignal periods to provide said sequence of master timing pulses duringeach measure of music.
 11. The combination according to claim 4 whereinsaid patterns of pulses comprise different groups of pulses selectedfrom a sequence of master timing pulses generated during each measure ofmusic, said master timing pulses being generated by: means forrepetitively generating a ramp signal waveform, there being a pluralityof ramp periods in each measure of music; means responsive to said rampsignal achieving respective amplitudes for generating a sequence ofprimary pulses during each ramp signal period; means for gatingpredetermined groups of said primary pulses during successive rampperiods in each measure of music; and means for combining the gatedprimary pulses to provide said sequence of master timing pulses.
 12. Ina system for controlling the rhythmic accompaniment pattern provided bya background instrument of the repetitive rhythm type: means forgenerating a fixed sequence of master timing pulses during each measureof music; means for at will selecting distinct arrays of said mastertiming pulses in correspondence with predetermined rhythmic patterns;generator means responsive to application of master timing pulsesthereto for generating musical tones; means for applying said selectedarrays of said master timing pulses to said generator means; and meansfor inhibiting application to said generator means of at least one ofsaid selected arrays of master timing pulses during randomly selectedmeasures of music.
 13. In a system for controlling the rhythmicaccompaniment pattern provided by a background instrument of therepetitive rhythm type during the performance of a musical composition:means for dividing each measure of said musical composition into 24equal time periods; means for generating a fixed sequence of mastertiming pulses for each measure, said master timing pulses being spacedby integral numbers of said time periods; means for at will selectingvarious distinct arrays of said master timing pulses in correspondencewith predetermined rhythmic patterns; and means responsive to saidselected master timing pulses for generating rhythmic sounds of diversecharacter.
 14. The system according to claim 13 wherein at least onegroup of four of said master timing pulses are equally spaced by six ofsaid time periods and wherein at least one group of three of said mastertiming pulses are equally spaced by eight of said time periods.
 15. Inthe system according to claim 13: wherein said means for dividingcomprises: a source of repetitive ramp waveforms, a fixed integralnumber of said ramp waveforms comprising a measure; and plural pickoffmeans, each adjusted to pick off a respective amplitude level of saidramp waveform; and wherein said means for generating comprises aplurality of pulse generators, each responsive to pickoff of anamplitude level by a respective pickoff means for generating a mastertiming pulse.
 16. The combination according to claim 15 wherein saidmeans for at will selecting comprises a matrix having a first group ofsignal lines, a second group of signal lines, means for couplingpredetermined ones of said first group of lines to predetermined ones ofsaid second group of lines; means for applying said master timing pulsesto respective ones of said first group of lines; means for connectingsaid second groups of lines to said means for generating, and means forselectively inhibiting signal conduction to said means for generatingalong specified ones of said second group of lines.
 17. The combinationaccording to claim 15 wherein said integral number is greater than one.18. The combination according to claim 13 further comprising selectivelyactuable means for alternating the selected array between two rhythmicpatterns at a frequency which is randomly related to the frequency ofsaid measures of said musical composition.
 19. The combination accordingto claim 13 wherein said means for generating rhythmic sounds includesgenerator means responsive to trigger signal thereto for generating amusical sound at constant amplitude for the duration of the appliedtrigger signal and at a decaying amplitude for a predetermined timeperiod immediately thereafter, said combination further comprising:means responsive to at least two time-spaced master timing pulses in atleast one selected array for applying trigger signal to said generatormeans during the entire time interval between said at least two pulses.20. The combination according to claim 19 and further comprising: meansfor applying master timing pulses from said selected arrays to saidgenerator means as trigger signals.
 21. In a rhythm accompaniment systemof the repetitive rhythm type: means for generating a fixed sequence ofmaster timing pulses during each measure of music; generator meansresponsive to application of trigger signal thereto for providing amusical tone with a predetermined constant amplitude for the duration ofsaid trigger signal and with a decaying amplitude for a predeterminedtime interval after termination of said trigger signal; means for atwill selecting distinct arrays of said master timing pulses incorrespondence with predetermined rhythmic patterns; means for applyingmaster timing pulses from said selected arrays to said generator meansas trigger signal; means responsive to at least two time-spaced mastertiming pulses in at least one selected array for applying a steadytrigger signal to said generator means during the entire time intervalbetween said at least two pulses.
 22. The combination according to claim21 wherein said means for generating includes a plurality ofindividually triggerable voice circuits, each responsive to applicationof trigger signal thereto for generating a sound which simulates thatproduced by a respective musical rhythm instrument, and wherein isfurther provided means for selectively gating pluses of said selectedarrays as trigger signal for predetermined ones of said voice circuits.23. The system according to claim 22 wherein said means for selectivelydistributing comprises a matrix comprising a first group of leads, asecond group of leads arranged orthogonally of said first group of leadselectrically coupling predetermined ones of said first group of leads topredetermined ones of said second group of leads, means for applyingsaid master timing pulses to respective ones of said first group ofleads, means for connecting said second group of leads to said means forselectively gating, and means for inhibiting conduction of master timingpulses to said means for selectively gating along selected ones of saidsecond groups of leads.
 24. In a system for controlling the rhythmicaccompaniment pattern provided by a background instrument of therepetitive rhythm type: a source of repetitive ramp waveforms, each rampwaveform having the duration of one-half measure of a musicalcomposition; means for deriving a sequence of primary pulses in responseto preselected amplitude levels along said repetitive ramp waveforms;means for deriving a sequence of secondary pulses by gatingpredetermined ones of said primary pulses during alternate ones of saidramp waveforms, said primary pulses and said secondary pulses comprisingA fixed sequence of master timing pulses for each measure; matrix meansfor at will selecting various distinct arrays of said master timingpulses corresponding with rhythmic patterns and applying the selectedmaster timing pulses to selected conductors of said matrix; and meansresponsive to said master timing pulses appearing on said selectedconductors for generating rhythmic sounds of diverse character.
 25. Thecombination according to claim 24 further comprising adjustable meansfor controlling the repetition rate of said ramp waveform.
 26. Thecombination according to claim 24 further comprising selectivelyactuable means for alternating the selected arrays between two rhythmicpatterns at a frequency which is randomly related to the frequency ofthe measures of said musical composition.
 27. The combination accordingto claim 24 wherein said master timing pulses are spaced by integralmultiples of a specified time interval, there being 24 of said fixedtime intervals in each measure.
 28. In a system for controlling therhythmic accompaniment provided by a background instrument of therepetitive rhythm type: a source of repetitive ramp waveforms, each rampwaveform having the duration of an integral submultiple of a measure ofmusic; means for deriving a sequence of primary pulses in response topreselected amplitude levels along said repetitive ramp waveforms; meansfor deriving a sequence of secondary pulses during each measure of musicby gating different groups of said primary pulses during successive rampwaveforms of each measure; means for at will selecting various distinctarrays of said secondary pulses corresponding with rhythmic patterns;and means responsive to said selected secondary pulses for generatingrhythmic sounds of diverse character.
 29. A voice circuit responsive toapplication of a trigger pulse thereto for providing a rhythmaccompaniment sound, said circuit comprising: a gated oscillator forselectively providing a first oscillatory signal having a firstfrequency; a continuous oscillator for continuously providing a secondoscillatory signal at a second frequency, higher than said firstfrequency; a common output junction; a linear gate circuit selectivelyactuable to apply said second oscillatory signal to said common outputjunction without distortion; control means responsive to said triggerpulse for: a. actuating said linear gate to pass said second oscillatorysignal to said common output junction at a constant amplitude for theduration of said trigger pulse and at a decaying amplitude for apredetermined time period after termination of said trigger pulse; andb. gating on said first oscillator to couple said first oscillatorysignal to said common output junction at a constant amplitude for theduration of said trigger pulse and at a decaying amplitude for a furtherpredetermined time period after termination of said trigger pulse. 30.The combination according to claim 29 wherein said first frequency isapproximately 1 kHz. and said second frequency is approximately 2 kHz.31. The combination according to claim 29 wherein said predetermined andfurther predetermined time periods are unequal.